386 M, C. Robin on the Sexual Differences of Eels. 



be two pale belts : in my specimen there are a few grey scales 

 on the portion of the wing corresponding to the interval be- 

 tween the first and second subbasal black belts in P. anti- 

 phates^ as also on the interno-median area near the outer 

 angle. The outer half of the second U-shaped mark, as also 

 the submarginal band, is sap-green instead of white. The hind 

 wing as in P. ■nebulosus. On the underside the fore wing is 

 marked as in P. nebulosus, i. e. differs from the upperside in 

 having the base, U-shaped markings, and submarginal band 

 all of a deeper shade of green, and the inner margin, together 

 with a large portion of the median area behind the third 

 median nervule (in fact, just that portion of the wing which 

 is covered by the hind wing when the insect is at rest with its 

 wings closed over its back), ashy white. Hind wing as in 

 Sikkim specimens of P. antijjhates, except that the area be- 

 tween the middle and outermost black bands is thickly 

 clouded, as if the bands bounding it had been "smudged" 

 over it, with black scales ; and the area beyond the cliscal 

 series of rounded black spots is also more or less clouded 

 with scattered black scales. Tlie specimen therefore differs 

 considerably from that upon which Butler has founded liis 

 P. nebulosus. In spite, however, of its many points of differ- 

 ence from P. nebulosus, and still more from P. antiphates, I 

 am exceedingly averse to calling it a new species, being of 

 opinion that it is, like the first-named species, only a melanoid 

 variety of P. antij)liates , or possibly rather a reversion to the 

 primordial type of coloration of the entire antijjliates group of 

 Papiliones. 



XXXVIII. — The Male Eels compared with the Females. 

 By C. Robin*. 



The existence of sexual differences in the common eel [Mui^ana 

 anguilla, l^.^Anguilla vulgaris, Rafinesque, Rondelet) is open 

 to no doubt, at whatever period of the year the examination 

 is made. 



With very few exceptions all the eels described under the 

 varietal name oi pimpeneauox pimperneau, from the maritime 

 pools and marshes {glut-eel of English authorsf) , with large 

 prominent eyes, a short flat muzzle, a slender cylindrical body, 



* Translated from tlie ' Comptes Rendus,' February 21, 1881, pp. 378- 

 383. 



t The broad-nosed eel, Anguilla latirostris, of Yarrell. 



